The invention relates to a device for reading out X-ray information stored in a storage phosphor layer.
One possibility for recording X-ray pictures is to the X-ray radiation passing through an object, for example a patient, as a latent picture in a so-called storage phosphor layer. In order to read out the latent picture, the storage phosphor layer is irradiated with stimulation light, and so stimulated into emitting emission light. The emission light, the intensity of which corresponds to the picture stored in the storage phosphor layer, is collected by an optical detector and converted into electrical signals. The electrical signals are further processed as required, and finally made available for analysis, in particular for medical/diagnostic purposes when they are displayed on an appropriate display unit, such as e.g. a monitor or a printer.
With generic devices according to the prior art, the detector signals produced by a detector when collecting the emission light are converted by an analogue to digital converter into digital detector signal values. The detector signal values obtained in this way are typically given with a 12 or 14 bit resolution, and this corresponds to a graduation of the detector signal values produced in maximum 4096 or 16384 levels.
So that the respective maximum possible resolution can be achieved when digitising the detector signals, the pre-amplification of the analogue detector signals is set before reading out a storage phosphor layer, dependent upon the height of the detector signals to be expected when reading out this storage phosphor layer. This setting is often undertaken taking into account the so-called Speed Class which is a measure for the X-ray dose stored in the phosphor layer when the X-ray is taken.
Because the aforementioned setting can be undertaken by an operator, operator errors can not be ruled out. If an operator error occurs, the X-ray information stored in the phosphor layer is not read out and digitised which the required resolution. The X-ray must then generally be taken again, and this results in the patient to be examined being subjected to additional radiation.
It is the object of the invention to provide a device for reading out X-ray information stored in a phosphor layer which overcomes the above and other shortcomings in the prior art.